Going underground

Think the swimming pool and tennis court in your garden make you pretty smart? Well, sorry, but that’s just so 20th century. These days, if you want to keep up with the oligarch next door, you put your play things under your London house.

Londoners have used their underground space for a long time. Winston Churchill had war rooms, Joseph Bazalgette dug sewers, and the capital’s cheerful commuters have enjoyed underground rail transport since 1863. In the last 20 years, however, advances in building and lighting technology have accelerated the rise (or, more accurately, descent) of a new underground trend: the mega-basement.

Big British houses have traditionally used basements as dank wine storage and dungeon space. Now, however, it’s possible to create several floors of light, spacious rooms underground. These might include, at the top end, ballrooms, galleries and swimming pools.

These mega-basements are serendipity for the drivers of the super-prime property market. London’s tiresome planning laws prevent you from knocking down your 17th-century palace and replacing it with a more functional skyscraper. This has long frustrated the expansion plans of men and women with a spare hundred million pounds or two.

Now, perhaps envious of steel man Lakshmi Mittal’s jewelled subterranean Kensington swimming pool, other London-dwelling tycoons such as Russian oil billionaire Leonid Blavatnik, estate agent Jon Hunt, and the Sultan of Brunei, as well as celebrities such as Take That’s Mark Owen, are planning and building underground lairs that mirror and sometimes even exceed the size and opulence of the mansions above them. Basement companies refuse to name names, but admit creating mega-basements for top-end bankers, business magnates, footballers and film stars.

Jon Hunt, founder of estate agents Foxtons, applied last year for five floors beneath his house (just across the way from Kensington Palace, Princess Diana’s old pad). Plans included a modest underground museum for his collection of vintage cars and motorbikes, and a tennis court. His plans were rejected – more on that later – but there are plenty more being built.

In Chelsea, 23 Cadogan Place (£24m, Savills), has an underground swimming pool, gym, steam room, staff bedroom and cinema. Over in Kensington, 23 Upper Phillimore Gardens (£35m, also Savills) has all those things, plus a wine cellar, large playroom and staff quarters, while 21 Grosvenor Mews in Belgravia has a car lift, garden with sliding roof, and, plunging the entire height of two above-ground and two subterranean floors, a nine-metre interior decorative “waterfall” of water trickling down bronze slabs (bought in December 2009 by a French businessman and his Russian wife for £7.5m, a record for a mews house).

Tom Tangney, partner at estate agents Knight Frank, says: “My favourite basement has a swimming pool with two deep ends so the owner can do tumble-turns. In the arched space beneath, there’s a vaulted wine cellar.” Other popular additions include swimming pools with sliding roofs, party rooms and spa facilities.

Derek Taylor, head of development control for the Royal Borough of Kensington and Chelsea, says: “Ten years ago, there were virtually no applications to dig large basements. Four years ago, it seemed that every second application was a basement conversion.” In the past three years, the borough granted 461 “digging-down” applications, rejected 42 and 66 are pending.

The basement boom began, strangely enough, in the genteel upper-middle class west London suburb of Fulham. “It all started in the late 1980s, on Fulham’s Peterborough Estate,” says Jeremy Fisher, whose firm Jeremy Fisher Building has been “digging down” since the craze began. “Traditionally, the British middle class didn’t spend much on kitting out houses. They’d be content with old central heating and mouldy bathrooms. That all changed in the 1980s. Fulham’s residents – mostly City bankers, lawyers and so on – looked to modernise and expand. Houses on Fulham’s Peterborough Estate already had large basements, so residents expanded downwards.”

Neighbours, keen to keep up with and overtake the Joneses, copied them – but on a larger scale. Because basements are pretty much invisible, they found that planners let them build a network of subterranean rooms taking up the entire “footprint” of their properties – ie underneath the house and garden.

Two main factors enabled and accelerated the trend. First, house price rises outstripped building costs, so digging down resulted in that great middle-class joy: a rise in house value. The second factor was the technology.

Basement living had hitherto been damp, dark and miserable, suited only to depressed students. But builders have vanquished damp by replacing semi-porous render with a waterproof plastic membrane around the basement. Instead of seeping through walls, water now drains to a sump, where a pump sends it to the sewers. Lighting was massively improved by the simple idea of light wells – small windowed courtyards taking sunlight to the basement, and higher-tech solutions such as fibre optics.

A decade or so ago, developers, spotting the trend in smaller houses, realised it could work on a massive scale, and looked towards Chelsea, Mayfair and Belgravia. Digging down costs are roughly the same here as in Fulham – £500 to £730 per sq ft. Houses in Fulham sell for £700 to £1,000 per sq ft, so the profit is good. Houses in central London zones such as Mayfair cost £1,700 to £2,500-plus per sq ft.

With few exceptions, nationally and internationally, digging down is peculiar to the smarter areas of London. Charles Weston Baker, head of Savills International says: “It’s due to our unique style of old cottages. Cities like Paris have large apartment blocks. In newer cities they don’t have listings, so they just replace old buildings.”

Theoretically, since they are invisible, basements fall under permitted development rights and are not subject to planning control. Guy Bransby, director of Jones Lang LaSalle, who devised Jon Hunt’s five-storey basement application, says: “If you can’t see something, it doesn’t make any difference.” In Hunt’s case, his London borough judged that creating such a vast underground area changed the character of a listed building, and so denied it.

“Neighbours hate it,” admits Jeremy Fisher. A survey by residents’ group The Ladbroke Association found many neighbours in Kensington and Chelsea who had been traumatised by the relentless noise and vibration of a dig-down. They suggest that neighbours should be compensated, or even rehoused at the digger’s expense.

There are more serious dangers than dust. In 2008 a London house collapsed during a dig-down, injuring a builder. Robert Sturges, director at estate agents Chesterton Humberts says: “I’ve heard horror stories, particularly when non-specialist builders are hired. On a couple of occasions, the neighbouring houses began to sink because of the lack of secure foundations. That was very expensive for the digger.”

There’s another dark side to basements, according to Anne Soutry of Savills: “The price has increased enormously over five years. It is profiteering on behalf of the basement companies.”

The final worry is that the creation of more London basements will have a negative effect on the water table and cause flooding. However, a study by engineering firm Arup found that digging down had had no effect on the water table, and there was no foreseeable reason why it should.

What is the future? Is basement living a fad, or an entrenched cultural shift? Certainly basement planning laws will eventually be centralised and formalised. This won’t prevent digging down, but it’s likely, according to builder Jeremy Fisher, to add dust and noise reduction requirements. This may hamper the families of Fulham, but it won’t stop the oligarchs.

Perhaps the only limit to mega-basements is developers’ and oligarchs’ imaginations. What’s next? A swimming pool that drains to reveal a helipad? A private underground rollercoaster? Perhaps in 20 years’ time we’ll see 20-storey “magma-scrapers” popping down all over London.

London Digs, www.londondigs.net, tel: +44 (0)20 7289 5599

The Big Basement Company, www.bigbasement.co.uk, tel: +44 (0)20 7096 7000

London Basement, www.tlbc.co.uk, tel: +44 (0)20 8847 9449

CC Construction, www.cccon.co.uk, tel: +44 (0)20 7376 7770

Jeremy Fisher Building, tel: +44 (0)20 7731 0716 (no website)

The Ladbroke Association, www.ladbrokeassociation.org, tel: +44 (0)20 7229 1741

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